How many more polymorphs of ROY remain undiscovered

Area of Science:

• Materials Science
• Crystallography
• Computational Chemistry

Background:

• 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile (ROY) has a record 12 characterized crystal polymorphs.
• Recent discoveries indicate potential for more ROY polymorphs, necessitating further investigation.

Purpose of the Study:

• To create the first comprehensive crystal energy landscape for ROY.
• To assess the likelihood of discovering new ROY polymorphs.
• To guide future experimental solid-form screening efforts.

Main Methods:

• Utilized crystal structure prediction techniques.
• Employed conformational energy-corrected density functional theory for accurate energy rankings.
• Analyzed lattice energies to map the ROY crystal energy landscape.

Main Results:

• The study generated an accurate ROY crystal energy landscape, aligning well with experimental data.
• Lattice energies indicate that most stable ROY polymorphs (7 of 9) on the Z'=1 landscape have been experimentally discovered.
• A new crystal form of ROY is predicted to be enthalpically stable above 10 GPa.

Conclusions:

• Discovering new ambient-pressure ROY polymorphs may require advanced crystallization methods.
• High-pressure experiments are recommended to explore predicted new ROY crystal forms.
• High-accuracy crystal structure prediction, with conformational energy corrections, is valuable for solid-form screening.